The Seroprevalence of Canine Influenza Virus H3N8 in Dogs Participating in a Flyball Tournament in Pennsylvania in 2010: A Follow‐Up Study

Abstract

Canine influenza virus (CIV) H3N8 infection is thought to be highly contagious and potentially deadly. Low seroprevalence in dogs participating in the sport of flyball in 2009 was reported. It remains unknown if prevalence is changing in dogs at risk. To determine seroprevalence of antibodies to CIV H3N8 in a population of pet dogs that participated in an indoor flyball tournament in Pennsylvania in November 2010. Dogs participating in a flyball tournament. Medical, travel, and activity histories for previous 10.5months were obtained from consenting owners and serum samples were collected from dogs. Antibodies to CIV H3N8 were measured using hemagglutination inhibition. Of 251 competing dogs, 103 dogs were tested. Overall, seroprevalence of CIV H3N8 in dogs participating in flyball was 1.9% (95% CI, 0.05-6.8%). Thirty-five dogs were tested in both 2009 (all titers <8) and 2010 (all titers <8). Ten of 103 dogs had been vaccinated for CIV H3N8. Two dogs had positive titers (>8) and both had been vaccinated twice in the previous month. Titers in remaining 8 vaccinated dogs were undetectable. Seroprevalence in vaccinated dogs was 20% (95% CI, 5.7-50.1%), whereas in unvaccinated dogs it was 0% (95% CI, 0-4.0%). Although 7 dogs had history of respiratory signs, only 1, which was vaccinated, was serologically positive for CIV H3N8. Consistent with low prevalence of CIV H3N8 exposure previously reported in flyball dogs, unvaccinated dogs had 0% prevalence, suggesting a stable exposure rate. However, low seroprevalence may result in unprotected flyball dogs at risk for developing CIV H3N8.